The allegations by Miroslav Naydenov, the ex-agriculture minister, have further fueled a surveillance scandal that has shaken the country before next month's general elections. Some media here are calling it "Bulgaria's Watergate."

In an interview with the private bTV channel Thursday, Naydenov didn't offer any evidence for his claims against ex-Interior Minister Tsvetan Tsvetanov. But he called on him to take responsibility and quit politics.

Tsvetanov, who now heads the election campaign of the ex-ruling party, has denied any wrongdoing.

Naydenov cited a meeting with President Rosen Plevneliev, saying that during the conversation the two left their cellphones in the room next door and switched the television on allegedly to avoid being wiretapped.

"Tsvetanov, you did it, the honest and politically responsible thing to do is to get off the political stage and clear your name if possible," Naydenov said.

He accused Tsvetanov of spying in order to blackmail everyone and eliminate all who would get closer to former Prime Minister Boiko Borisov. Naydenov suggested that Borisov could have been subject to wiretapping as well.

Naydenov is the subject of an investigation into alleged impropriety while in office as agriculture minister. He has denied the allegations.

Tsvetanov told reporters Thursday that "special surveillance means have been used only in keeping with the law. Everything I did (as interior minister) has been in the best interest of the state."

He also said that the timing of Naydenov's accusations about the unlawful wiretapping of politicians, journalists and public figures has not been picked randomly and came right at the start of the election campaign.

Prosecutors recently pressed charges against four former police officials accused of involvement in wiretapping political opponents of the former center-right government, which stepped down amid public unrest in February. They have summoned Naydenov as a witness.

"The witness confirmed his statements made in the TV interview, and provided additional details which we cannot reveal now," Rumyana Arnaudova, spokeswoman of the Sofia prosecutor's office, said.

The prosecution announced also that Naydenov had asked for guarantees for his own security and will be placed under security watch.

Naydenov told the TV station that he had sent his family abroad to keep it away from trouble.